What Is QoS?

QoS, or Quality of Service, is a method for controlling traffic
priority on networks. It works on all levels of network activity, but
for our purposes, it’ll be centered around your home router. There, QoS
kicks in when there’s a bottleneck and decides which traffic is more
important than the rest. Exactly what is more important then the rest is
based on rules that you supply. You can specify importance based on
criteria such as IP address, MAC address, and even service name.

Where’s the Bottleneck?

Many people set up QoS hoping that it’ll do a lot of good only to
report later that it doesn’t do anything. That’s because QoS only works
when the bottleneck is in the right place, and the key settings are your
bandwidth declarations.
Suppose that your QoS settings are set beyond the bandwidth you
receive from your ISP. What happens is that the traffic that leaves your
router isn’t prioritized because your router thinks that there’s ample
bandwidth available. Meanwhile, you’re hitting your ISP’s caps, and
they’re the ones who decide what is and isn’t important.
On the other hand, if you set your QoS’s declared bandwidth lower than your allotted ISP bandwidth,
you’re creating an artificial bottleneck where you can control it: at
your router. Now, your own QoS settings kick in and re-arrange your
traffic. The cost of bandwidth is pretty minimal, but by tweaking things
slowly you can marginalize it further.

Tweaking Steadily

The key to getting your bandwidth back is tweaking and observing over time. The Uplink and Downlink settings are your keys.
Start by taking a bandwidth test to find out what your normal speeds
are from your ISP. There are numerous tests out there, such as Speakeasy Speed Test and SpeedTest.net.
We suggest you start your QoS dabbling by setting these values to 85%
to ensure that your QoS is being effective. Once you tweak your
settings until things work the way you want them, you need to take the
next step and ramp things up bit by bit.
Take your Downlink and Uplink and boost them by 1-2% at a time,
preferably while maxing out your bandwidth and checking your QoS
settings to make sure they’re still in effect. It’s possible to go as
high as 95% percent and still have your bandwidth prioritization
working. Kick things up by an increment and give it a few days. Lather,
rinse, repeat. You can reclaim quite a bit of sacrificed bandwidth this
way